Jump to content
HybridZ

Just for he heck of it


Recommended Posts

I just put a Tunnel ram with 2 holley 450's on my Z. Got it fired up last night. Don't know how it's going to perform but it looks nasty. I have a short video clip of it idling in the driveway (about 8 meg), but have no place to host it. Can I e-mail it to someone and get it up here?

 

Thanks

Jeff

Link to comment
Share on other sites

Yes the link works, it sounds good and throughty. I am a big fan of dual carbs and a tunnel ram. That is what I used to run before stepping up to a blower / supercharger. Just to mention if you have not done it, besure to check your vacumm as far as power valves, you might have to go with a smaller ones or block them off.

 

John

Link to comment
Share on other sites

Thanks John, please expand on the vacuum comment. I got the carbs (450 CFMs) off e-bay from a guy who was runing them on a SBC stroker. I just slapped them on there and fired it up. Hopefully they are pretty close but I have not tuned them at all. This kind of setup is new to me so I don't even know where to start.

Link to comment
Share on other sites

I also love the way a correctly tuned dual quad set up sounds and runs, dual quads are seldom used in my opinion mostly becuase most guys won,t take the time to learn how to tune them, its not because theres any power loss!

in fact I regularly make excellent power with dual quads

 

the problem is NOT tuning the dual quads, that can be done very easily with experiance , the reason many low rise dual quad systems don,t make the potential peak power is the RUNNER length, twisting routes,and differant runner lengths/ design and cross sectional area of the intake designs, like this

5425.jpg

which,while they work great in the mid rpm ranges don,t produce peak power

the design tends to restrict/break up, air flow and the ram effect that pacts the cylinders at high rpms and effect flow rate changes beween cylinders compared to a single plane design with its LONGER and STRAITER ports

but there are dual quad intakes with longer/straiter runners

crossram-edelbrock-tops-42p.jpg

crossram-offy-tops-42p.jpg

 

THere ARE EXCEPTIONS that work reasonable well! like the cross ram intakes above!

 

read this

http://victorylibrary.com/mopar/intake-tech-c.htm

 

now THATS not true on the better TUNNEL RAM intake designs BUT hood clearance and thier designed effective rpm range cause them to be less than IDEAL on the average street car

 

the reason DUAL QUADS were popular years ago was that large flow CFM single 4 barrel carbs were not available,at that time,HOLLEY had not yet produced the DOMINATOR carbs, that could flow 1250 CFM,if your engine needed 850cfm-1200 PLUS cfm, in the early 60s you were either using a DUAL quad or similar multi carb system or you were NOT getting the flow rates you needed,or you were stuck with QUADRAJETS, or the smaller HOLLEYS in most cases

 

and yes your correct two smaller carbs with eight throttle bores can and do allow a very precise high velocity port flow when properly set up,Ive had several engines running dual quads run VERY respectable times in the low 10s, in a STREET DRIVEN CARs once SLICKS and OPEN headers were used at the track

Link to comment
Share on other sites

how YOU start

 

start by checking for vacuum leaks,and setting the acellerator pump shot to maximum,and BY JETTING ALL 8 carb VENTURIES THE SAME AND SETTING UP BOTH CARBS TO OPEN EXACTLY AT THE SAME RATES. (personally I prefer to set all 8 venturies open equally for racing) you need to equalize the flow rates and minimize the turbulance and fuel/air distribution potential problem areas,

BTW heres where

a infared non-contact thermometer helps diagnose mixture problems very quickly, but youll need one that reads into the 1400F range for the headers for quick diagnoses

you can forget about vacuum advance on the ignition or vacuum brakes as the readings will be low on any correctly set up system, youll also need to learn a slightly differant launch tech. as you generally can,t FLOOR the carbs and hang on, youll need to push the petal to the floor slightly slower allowing the engine to smoothly transition

 

http://www.professionalequipment.com/xq/ASP/ProductID.3461/id.22/subID.177/qx/default.htm

Link to comment
Share on other sites

Great stuff Grumpy, I can't wait to get some free time to start studying. Have basically bolted the thing up and drove it around the block. I did check my vacuum last night. My 450's have one vacuum port (pretty high up on the body) but my results were strange. One carb was showing little to no vacuum (maybe 1 or 2 psi) and the other was pulling about 12 psi. Again, I haven't even turned a screw on these things as I really wasn't sure where to start. All in all, it runs good, idles good and takes off good. I have already figured out your comment about you can't stomp it, but if you roll into it it sings!

 

thanks

Jeff

Link to comment
Share on other sites

tunnel rams generally run best with a tight 104-106 lca and a durration in the 230-250 range, Ive had excellent results with the CRANE 110921 on 350- 383s but youll need about 10.5:1-11.5:1 cpr and 3.73-4.56:1 rear gears , and a manual trans or a 2800rpm-3200rpm stall converter to get the full benefits

 

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=110921&lvl=2&prt=5

Link to comment
Share on other sites

LOTS of notes from 35 plus years of previous engine builds and EXPERIANCE, plus having worked on literally hundreds of muscle cars helps WHY? have you ever found ANY advice to be WRONG??

btw the whole object of using a tunnel ram is to MAXIMIZE the cylinder fill efficiency in the 4000rpm AND ABOVE rpm range, useing direct port ram tuning

so the cam timing must match that rpm band and the compression must match the cam timing for it all to work.

Link to comment
Share on other sites

Link to comment
Share on other sites

This seems strange to me, I was checking my vacuum yesterday and at idle, I get about 8 psi at the manifold and between 1 and 4 at the carb (depending) on which one I check. Anyway, when I rev it up, the vacuum climbs. I didn't go WOT but the more I revved, the more vacuum it pulled at both locations. That's not right is it??

 

Grumpy, I have not checked my power valves yet to see if that's why I have the low vacuum on one carb. Maybe tonight.

Link to comment
Share on other sites

Oops, I was just reading on Edelbrock's web site and under my manifold it list that the 9776 holley (what I have) is used for sideways mount only. I have mine mounted straight. Can someone explain why they would have to be sideways mounted? Dang I made some nice linkage parts that won't work if I turn them!

Link to comment
Share on other sites

is your intake manifold manufactured by EDELBROCK??? or a differant manufacturer??

carb mounting locations and clearances DO VARY between manufacturers

example, some weiand intakes have greater spacing and allow either mounting style

 

I mount those carbs like you have done, but on some intakes THEY won,t fit due to clearance issues, so you need to mount sideways like the DOMINATOR CARBS

 

as to the vacuum readings going up, thats NORMAL if the carbs are opening slightly slower than the engines rpms and intake port requirements build due to the increased rpms (a good thing on the street) but you MIGHT want to increase the rate the carbs open on a race application,as it indicates a slight restriction to flow(TEST/TUNE & EXPERIMENT)generally youll WANT the intake to pull a MINIMUM of 1-1.5 inches at full W.O.T. (venturies fully open)for a street car, and it usually won,t hurt much on a race car

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...